Women are working in the labor market later into pregnancy and returning to work sooner after childbirth than ever before. The proposed research will investigate the magnitude, causes and effects of recent mothers, labor supply during the perinatal period. The research will use data from the Current Population Survey and from the National Longitudinal Survey of Youth to: *Construct new aggregate time-series that more accurately track women's actual time at work in the months immediately preceding and following the birth of a child. These new time-series will distinguish between having a job and being at work; between paid and unpaid leave; and between full-time and part-time work. These new time-series will more accurately reveal the extent of actual change in the labor supply of mothers over the last two decades. *Estimate the determinants of mothers' labor supply near birth and examine the factors that explain the large secular change in women's labor supply following childbirth. *Evaluate how public policies such as state Disability Compensation regulations, Maternity Leave legislation, and AFDC regulations affect women's labor supply during pregnancy and after birth. *Examine the mechanisms through which women alter their labor supply after the birth of a child (e.g., part time work, change in occupations). *Study the consequences of women's labor supply decisions near childbirth on later wages.